The present invention relates to an apparatus for automating the construction of boats and more particularly to an apparatus for fabricating hull sections suitable for the construction of submarines utilizing automated laser welding equipment.
Since the early 1970's a considerable effort has been made by the boat building industry to improve productivity and reduce boat construction costs. A large part of this effort has been directed to the introduction into the boatyards of automated equipment and highly mechanized assembly line production systems where emphasis has been directed to precutting components, fabricating large subassemblies from the components and constructing the boat with the subassemblies using modular techniques.
In the construction of submarine hulls, high strength alloy steel plates are preassembled in sections and welded together forming the exterior shell of a hull subassembly. Circular T-frames are welded to the interior surface of the shell providing circular reinforcement of the shell to form the hull subsection. The welding of the T-frame to the shell is typically performed in a boatyard using a mechanized gas metal arc process. An essential requirement of this process is the preheating of the areas of be joined which is typically performed in the boatyard with thermostatically controlled electric strip heaters. The surface temperature of both the T-frame and the shell must be monitored during the operation to ensure that it is within the required range to obtain adequate welds, typically ninety to one hundred fifty degrees Celsius. This is a time consuming and costly portion of the boatyard welding process.
Additionally during the welding process many passes of the arc welder over the junction of the T-frame and the shell are required to obtain full penetration therein to form an acceptable weld. After each pass surface oxide, formed during the pass, must be removed from the weld area to avoid contaminating the weld during subsequent passes. Moreover, after a weld has been obtained on one side of the junction of the T-frame with a shell, the hull subsection must be inverted to form a weld on the other side of the junction since acceptable welds are typically obtained only when the welding is performed in a downhand direction. Because of the exceptional quality of the weld which must be obtained for submarine construction, the welding of T-frame supports to the interior surface of the shell to form hull subassemblies utilizing a metal arc welding process is a very time consuming and expensive process.